1. Field of the Invention
The present invention relates to the field of electronic instrumentation, and more particularly to instrumentation for monitoring the rate of usage of a particular utility.
2. Prior Art
Various types of utility monitors are very well known in the prior art. Typical examples are the water meters, gas meters and electric meters generally found on the supply lines to homes and other structures. These common utility meters for water and gas typically have some mechanical part which rotates in response to the flow through the meter, with the rotation being geared down in decades to drive a series of pointers for indicating the consumption in appropriate units, such as gallons or cubic feet. Such meters must be located in the main supply line to be useful for billing purposes, and normally are located outside of any structure so that they may be read without gaining access to the building. Accordingly, such meters are generally not located in a convenient location for reading by the persons actually using the utility, and further do not indicate either the accumulative cost of the utility used or the rate of increase of that cost. Electric power meters are similar, in that a member is electrically driven in rotation at a rate proportional to the power being consumed, the rotation being geared down to drive indicators for accumulating the total energy consumed.
Various meters have been proposed for monitoring a particular utility and providing a numerical readout in dollars and cents rather than in some unit of measure of the utility itself, such as watt-hours (electrical energy), cubic feet (natural gas), etc. These systems generally have a number of disadvantages, however, as they are typically integral with the basic utility monitoring device. By way of example, gear ratios may be changed and dials used to indicate dollars and cents so that an otherwise conventional meter may be used to measure directly in terms of cost of the utility. However, such meters are generally inconveniently located for monitoring purposes, are intended to be used in place of rather than in addition to a conventional meter readout, and the charge per unit of the utility is not easily changed if necessary. Examples of such meters are those disclosed in U.S. Pat. Nos. 796,033, 796,040 and 875,238. Other variable rate meters are also shown in U.S. Pat. Nos. 2,469,673 and 3,683,343.
In U.S. Pat. No. 3,311,824, a device for sensing the rotation of a watt-hour meter element is disclosed. Also, load monitoring and/or control systems for controlling total energy consumption in any given time period are disclosed in U.S. Pat. Nos. 2,994,038, 3,502,980, 3,505,508, 3,552,421, 3,602,703 3,652,838 and 3,872,286.